[BUGFIX] check if all sorting parts are present before access

Fixes: #3874
Ports: #3876
Replaces: #3875

Author: schugabe

Classes/Domain/Search/SearchRequest.php

@@ -350,7 +350,9 @@ public function getSeperatedSortings(): array
 
         foreach ($explodedSortings as $sorting) {
             $sortingSeperated = explode(' ', $sorting);
-            $parsedSortings[$sortingSeperated[0]] = $sortingSeperated[1];
+            if (count($sortingSeperated) === 2) {
+                $parsedSortings[$sortingSeperated[0]] = $sortingSeperated[1];
+            }
         }
 
         return $parsedSortings;